Panasonic bit sounds suspect, they make nothing APS-C and never have. Nevertheless, an interchangeable X is plausible. Though investing in new APS-C electronically-coupled Leica lenses sounds like a stretch even to me. Unlike M, if they doesn't get traction, you'll be stuck with some undoubtedly premium-priced stuff that you won't be able to use on anything else ever.

One possibility is the new aps-c sensor to be used in the upcoming 4K Panasonic Varicam, or a variant thereof. A continuation of Panasonic's professional Varicam video camera series, this will have a Super-35 (aps-c approx) size sensor.

As much as I would want Leica to stick with sensor larger than aps-c, a Leica branded m43 Panasonic, or a Leica-designed m43 camera built by Panasonic, could make some sense. There is an existing line of Leica branded Panasonic lenses for m43, and new lenses are being announced on a fairly regular basis. The new f1.2 Nocticron and f1.7 Summilux are part of that. They could redesign the Pana Leica 25mm to have an aperture ring, perhaps OIS, and it will be in keeping with these new lenses. Add a very high quality wide, like a 12mm f1.4, perhaps, maybe even a 10.5mm f1.4, and a Pana/Leica lens line could have a really good foundation.

Having said all of that, I would prefer Leica to stick with their core competencies, which revolve around the M system and lens design. An ILC from Leica is going to have to compete with every other aps-c and m43 system out there, and if the X series is any indication, the Leica system will be three times as much and offer features and operational performance two or three years behind the competition. Most likely, image quality will be tops, handling will be great if you enjoy Leica M handling, but in 2015 it would probably feel like a camera from 2011 or worse.